SBR "U" (Page 45)

For behind the saddle,

1 bottle: http://xlab-usa.com/delta-300.html

2 bottles: http://xlab-usa.com/sonic-wing.html

(you have to buy gorilla or chimp cages separately if you get the 2 bottle mount)

The x-lab bottle cages are pricey but they really don't launch.

For seat tube on a small bike, check with your shop, but a side-entry cage might work.  There are several others; I'm a fan of xlab

http://xlab-usa.com/sidekick.html

Edit: btw, the sidekick cage has a left and right version, but that's for the down tube.  If you put it on the seat tube, get the opposite one (left, if you're right-handed).

I also have an x-lab sonic wing mounted behind the saddle with two bottle cages (with one bottle cage and regular bottle mounted between my aero bars).  I have lost one bottle from the rear set-up -- it was in a race with bumpy roads.  I don't know when I lost it, but I reached back to grab it and realized it was gone.  Anyways, now when I go over bumpy sections (for example, there's a couple sets of railroad tracks we go over, where I've seen people eject bottles in the past), I reach back and check if they're still securely in place.

As for being able to grab bottles from behind you, it's a skill you'd have to work on, but it can be done....trust me, I'm not exactly the most coordinated and I can now do it without even leaving aero!  Practice it on the trainer before practicing it outside. 

I've used duct tape strips on the inside of the cages to help things hold better. Also got in the habit of checking the bottles every now and then.

I haven't done a race long enough to warrant this in some time. Long rides I've just used a camelbak or it was an event and 2 bottles has been fine, refilling at the various stops.

Anyway, In your case I would probably just zip tie a singe bottle behind the seat (the more horizontal you get it the less likely it is to eject, and it is most likely faster), and put one on the frame (if you only can fit one) and one BTA,then if you need a 4th put it in your jersey. Since you mentioned it, the front triangle on my road bike is smallish, and I do use the "side kick" bottle holders. They make the black ones in left and right versions, so you can mount them to the seat and down tubes and still have them release to the same side (you need a left and right as one is mounted backwards from the other) - this is the way my wife's bike is set up. I wanted white ones, and those only come in "right" so the one on the down tube releases to the right and the one on the seat releases to the left. The things we do for vanity!

The former, sort of. I race for one of the two tri-specific "pro" shops in town. I think they both have similar arrangements with their sponsored athletes: no fee to be a team member like club teams, but there is a competitve annual application process where they look at race performance and activity/visability in the local multisport community. For podiums (OA, masters, and AG) we get race fees cash reimbursed. We also get additional store credit for podiums, tiered according to placement. We get a regular 15% store discount anytime and once a year what they call our "pro" deal: 35% off anything they carry or can order. We are just not allowed to sell any pro-deal items for 12 months. We get a bike fitting each year from one of the best guys around, and all kinds of training and racing kit up. This year we got two tri kits, two road kits, racing singlets, t-shirts, visors, a hoodie, and even a trucker cap!

As our responsibility we have 10 team races of which we have to do at least 5, and 4 cycling and 4 running events of which we have to do at least one of each. We also do a team charity event every year, and have to volunteer for at least one race each season. It is a pretty good gig all-around.

Can you just ziptie something behind the saddle?  Depending on how you have it setup it can work very well.

Yup, just a cage ziptied to the saddle.  Something like this.

Here is mine as well - just like Arend's. 3 heavy tiptoes.

A little bit of trouble you may run in to depending on how your seat is positioned is that the p2 seatpost flares out at the top. If your seat is slid way forward it might get in the way of the cage somewhat.

Can you post a picture of what your saddle and seatpost look like?  I'm thinking you probably want to attach it to the saddle rails at least once to avoid slippage.

Your saddle position in relation to the seat post looks very similar to my 2007 P2.  I cannot zip tie a cage to the saddle rails because of this, and I think you may run into the same troubles as I did.  It looks like your best bet will be some form of wing that attaches to the two holes as Marc mentioned.

As far as cages, $20 for Specialized Rib cages.  Just trust me on this one.